U.S. patent application number 10/572328 was filed with the patent office on 2007-05-03 for high purity zinc oxide powder and method for production thereof, and high purity zinc oxide target and thin film of high purity zinc oxide.
This patent application is currently assigned to Nikko Materials Co., Ltd.. Invention is credited to Yuichiro Shindo, Kouichi Takemoto.
Application Number | 20070098626 10/572328 |
Document ID | / |
Family ID | 34419153 |
Filed Date | 2007-05-03 |
United States Patent
Application |
20070098626 |
Kind Code |
A1 |
Shindo; Yuichiro ; et
al. |
May 3, 2007 |
High purity zinc oxide powder and method for production thereof,
and high purity zinc oxide target and thin film of high purity zinc
oxide
Abstract
Provided is a manufacturing method of high purity oxide powder
including the steps of subjecting a raw material such as
Zn-containing scrap to acid leaching or electrolytic extraction,
thereafter performing solvent extraction and activated carbon
treatment thereto in order to remove impurities, neutralizing the
resultant solution freed of impurities with an alkaline solution to
obtain zinc hydroxide, and firing the zinc hydroxide to obtain zinc
oxide. Provided are high purity zinc oxide efficiently freed of
impurities, in particular C, Cl, S and Pb impurities, at low cost
and the manufacturing method thereof; a target manufactured by
firing the high purity zinc oxide; and a high purity zinc oxide
thin film obtained by the sputtering the target.
Inventors: |
Shindo; Yuichiro; (Ibaraki,
JP) ; Takemoto; Kouichi; (Ibaraki, JP) |
Correspondence
Address: |
HOWSON AND HOWSON
SUITE 210
501 OFFICE CENTER DRIVE
FT WASHINGTON
PA
19034
US
|
Assignee: |
Nikko Materials Co., Ltd.
10-1, Toranomon 2-chome Minato-ku
Tokyo
JP
105-0001
|
Family ID: |
34419153 |
Appl. No.: |
10/572328 |
Filed: |
September 8, 2004 |
PCT Filed: |
September 8, 2004 |
PCT NO: |
PCT/JP04/13031 |
371 Date: |
March 17, 2006 |
Current U.S.
Class: |
423/622 ;
204/298.13 |
Current CPC
Class: |
C23C 14/3414 20130101;
C01G 9/04 20130101; C01P 2006/80 20130101; C01G 9/003 20130101 |
Class at
Publication: |
423/622 ;
204/298.13 |
International
Class: |
C01G 9/02 20060101
C01G009/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 30, 2003 |
JP |
2003-339317 |
Claims
1. (canceled)
2. High purity zinc oxide powder having an impurity content
excluding gas components of N, C, Cl, S and P of less than 10 wtppm
and a total content of gas components of C, Cl and S of less than
100 wtppm.
3-6. (canceled)
7. A manufacturing method of high purity zinc oxide powder
including the steps of subjecting a raw material such as
Zn-containing scrap to acid leaching or electrolytic extraction,
thereafter performing solvent extraction and activated carbon
treatment thereto in order to remove impurities, neutralizing the
resultant solution freed of impurities with an alkaline solution to
obtain zinc hydroxide, and firing the zinc hydroxide to obtain zinc
oxide.
8-9. (canceled)
10. High purity zinc oxide powder according to claim 2, wherein
said powder has an impurity content of Pb of less than 5 wtppm.
11. High purity zinc oxide powder according to claim 10, wherein
said powder has a content of Mg and Al of less than 1 wtppm,
respectively.
12. High purity zinc oxide powder according to claim 2, wherein
said powder has a content of Mg and Al of less than 1 wtppm,
respectively.
13. A high purity zinc oxide sputtering target having an impurity
content of N, C, Cl, S and P, excluding gas components, of less
than 10 wtppm and a total content of gas components C, Cl and S of
less than 100 wtppm.
14. A sputtering target according to claim 13, wherein said zinc
oxide target has a crystal grain size of 100 .mu.m or less.
15. A sputtering target according to claim 13, wherein said target
has a content of Mg and Al of less than 1 wtppm, respectively.
16. A sputtering target according to claim 13, wherein said target
has an impurity content of Pb of less than 5 wtppm.
17. A sputtering target according to claim 16, wherein said target
has a content of Mg and Al of less than 1 wtppm, respectively.
18. A sputtering target according to claim 17, wherein said zinc
oxide target has a crystal grain size of 100 .mu.m or less.
19. A high purity zinc oxide thin film having an impurity content
of N, C, Cl, S and P, excluding gas components, of less than 10
wtppm and a total content of gas components C, Cl and S of less
than 100 wtppm.
20. A thin film according to claim 19, wherein said zinc oxide thin
film has a crystal grain size of 100 .mu.m or less.
21. A thin film according to claim 19, wherein said thin film has a
content of Mg and Al of less than 1 wtppm, respectively.
22. A thin film according to claim 19, wherein said thin film has
an impurity content of Pb of less than 5 wtppm.
23. A thin film according to claim 22, wherein said thin film has a
content of Mg and Al of less than 1 wtppm, respectively.
24. A thin film according to claim 23, wherein said zinc oxide thin
film has a crystal grain size of 100 .mu.m or less.
25. A high purity zinc oxide powder according to claim 2, produced
by a process comprising the steps of subjecting a raw material such
as Zn-containing scrap to acid leaching or electrolytic extraction,
thereafter performing solvent extraction and activated carbon
treatment thereto in order to remove impurities, neutralizing the
resultant solution freed of impurities with an alkaline solution to
obtain zinc hydroxide, and firing the zinc hydroxide to obtain zinc
oxide.
26. A method according to claim 7, wherein the grain size of the
zinc oxide powder produced by the method is 0.1 to 100 .mu.m.
27. A method according to claim 7, wherein the zinc oxide powder
produced by the method has an impurity content of N, C, Cl, S and
P, excluding gas components, of less than 10 wtppm and a total
content of gas components C, Cl and S of less than 100 wtppm.
Description
TECHNICAL FIELD
[0001] The present invention pertains to high purity zinc oxide
powder and the manufacturing method thereof, a sputtering target
obtained by firing this high purity zinc oxide powder, and a high
purity zinc oxide thin film formed by sputtering this target.
BACKGROUND ART
[0002] Zinc oxide (ZnO) is white-colored powder, also known as zinc
flower or zinc white, and is powder having hexagonal crystals.
[0003] Zinc oxide is used as white pigment for paint and artists'
colors, and is also used as pharmaceuticals or cosmetics. Further,
in recent years, zinc oxide is being used as a sputtering target
material for forming thin films to be used in electronic components
such as a semiconductor device.
[0004] Commercially available zinc oxide has a purity level of 95
to 99.9 wt %, and it is necessary to purify this further to obtain
a purity level of 4N to 5N. In particular, C, Cl and S must be
sufficiently reduced since these respectively form carbide,
chloride and sulfide together with Zn.
[0005] As conventional technology, there is a method of collecting
Zn from Zn-containing dust, and, with this method, Zn-containing
dust containing Fe and Pb is leached with sulfuric acid solution,
and subject to solvent extraction with D2EHPA. With this
technology, although there is an effect in the removal of Fe, there
is a problem in that Pb, Si and Al cannot be sufficiently removed
(e.g., refer to Patent Documents 1 and 2).
[0006] Further disclosed is a wet generation method of zinc oxide
for directly generating zinc oxide in a solution by neutralizing an
aqueous solution containing zinc salt in antalkali (refer to Patent
Document 3). Nevertheless, there is no particular description
regarding the removal of C, Cl, S and Pb, and it is also speculated
that this is accepting the existence of C, Cl, S and Pb.
[0007] Meanwhile, since high purity zinc having a purity level of
6N exists, it is also possible to consider oxidizing this to obtain
high purity zinc oxide. Nevertheless, since this will become
extremely costly, it is not realistic for industrial manufacture.
[0008] [Patent Document 1] [0009] Japanese Patent Laid-Open
Publication No. S59-116339 [0010] [Patent Document 2] [0011]
Japanese Patent Laid-Open Publication No. S59-126729 [0012] [Patent
Document 3] [0013] Japanese Patent Laid-Open Publication No.
S53-116296
DISCLOSURE OF THE INVENTION
[0014] Thus, an object of the present invention is to provide high
purity zinc oxide and the manufacturing method thereof in which
impurities, in particular C, Cl, S and Pb impurities, can be
efficiently removed at low cost by subjecting Zn-containing raw
material to acid leaching or electrolytic extraction, and
thereafter subject this to solvent extraction and activated carbon
treatment. Another object of the present invention is to provide a
target obtained by firing this high purity zinc oxide, and a high
purity zinc oxide thin film obtained by sputtering this target.
[0015] The present invention provides: [0016] 1. High purity zinc
oxide powder, high purity zinc oxide sputtering target and high
purity zinc oxide thin film wherein the impurity content excluding
gas components of N, C, Cl, S and P is less than 100 wtppm; [0017]
2. High purity zinc oxide powder, high purity zinc oxide sputtering
target and high purity zinc oxide thin film wherein the impurity
content excluding gas components of N, C, Cl, S and P is less than
10 wtppm; [0018] 3. High purity zinc oxide powder, high purity zinc
oxide sputtering target and high purity zinc oxide thin film
according to paragraph 1 or paragraph 2 above, wherein the total
content of gas components of C, Cl and S is less than 100 wtppm;
[0019] 4. High purity zinc oxide powder, high purity zinc oxide
sputtering target and high purity zinc oxide thin film according to
any one paragraphs 1 to 3 above, wherein the Pb content as
impurities is less than 5 wtppm; [0020] 5. High purity zinc oxide
powder, high purity zinc oxide sputtering target and high purity
zinc oxide thin film according to any one paragraphs 1 to 4 above,
wherein Mg and Al are respectively less than 1 wtppm; [0021] 6.
High purity zinc oxide sputtering target and high purity zinc oxide
thin film according to any one paragraphs 1 to 5 above, wherein the
crystal grain size of zinc oxide is 100 .mu.m or less; [0022] 7. A
manufacturing method of high purity zinc oxide powder including the
steps of subjecting a raw material such as Zn-containing scrap to
acid leaching or electrolytic extraction, thereafter performing
solvent extraction and activated carbon treatment thereto in order
to remove impurities, neutralizing the resultant solution freed of
impurities with an alkaline solution to obtain zinc hydroxide, and
firing the zinc hydroxide to obtain zinc oxide; [0023] 8. The
manufacturing method of high purity zinc oxide powder according to
any one of paragraphs 1 to 5 above, including the steps of
subjecting a raw material such as Zn-containing scrap to acid
leaching or electrolytic extraction, thereafter performing solvent
extraction and activated carbon treatment thereto in order to
remove impurities, neutralizing the resultant solution freed of
impurities with an alkaline solution to obtain zinc hydroxide, and
firing the zinc hydroxide to obtain zinc oxide; and [0024] 9. The
manufacturing method of high purity zinc oxide powder according to
paragraph 7 or paragraph 8 above, wherein the grain size of zinc
oxide powder is 0.1 to 100 .mu.m.
EFFECT OF THE INVENTION
[0025] The present invention yields a superior effect in that high
purity zinc oxide can be manufactured at low cost by dissolving a
zinc-containing raw material having a purity level of 90 to 99.9 wt
% with acid, and thereafter subjecting this to solvent extraction
and activated carbon treatment in order to effectively remove
impurities.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a flowchart showing the manufacturing method of
high purity zinc oxide.
BEST MODE FOR CARRYING OUT THE INVENTION
[0027] Examples of analytical values of the zinc-containing raw
material are shown in Table 1. As shown in Table 1, this raw
material contains Pb and Fe at 100 wtppm or more; Cu, Cd, Th, Mg,
Na, B and Li at roughly 10 to 80 wtppm; impurities such as Ni, Co,
Sn, Sb, W, Mo, Ga and Co respectively at roughly 1 to 10 wtppm; and
gas components of N, C, Cl, S and P at roughly 50 wtppm to 3 wt %.
TABLE-US-00001 TABLE 1 Impurities Raw material Example 1 Example 2
Example 3 Pb 100 <0.1 0.2 0.5 Fe 115 <0.1 <0.1 0.3 Cr 8
<0.1 <0.1 0.1 Ni 6 <0.1 <0.1 <0.1 Cu 10 <0.1
<0.1 <0.1 Al 5 0.3 <0.1 <0.1 Cd 20 0.2 <0.1 <0.1
Sn 5 0.3 <0.1 <0.1 Sb 1 <0.1 <0.1 <0.1 W 1 <0.1
<0.1 <0.1 Tl 35 0.1 0.2 0.7 Mo 2 <0.1 <0.1 <0.1 Ga 1
<0.1 <0.1 <0.1 Co 3 <0.1 <0.1 <0.1 Mn 1 <0.1
<0.1 <0.1 Ti 4 <0.1 0.3 <0.1 K 5 <0.1 0.3 <0.1 Mg
13 <0.1 0.2 <0.1 Na 80 <0.1 0.2 <0.1 B 10 <0.1 0.2
<0.1 Li 50 <0.1 0.2 <0.1 N 2000 100 70 300 C 1% 50 80 30
Cl 500 3 10 30 S 3% 8 20 50 P 50 <0.1 <0.1 <0.1 Number of
5 7 10 Particles
[0028] As described above, in particular, as a sputtering target or
thin film to be used in electronic components such as a
semiconductor device, high purity zinc oxide powder having a purity
of 99.99 wt % or more is required. In particular, it is necessary
to reduce impurities excluding gas components of N, C, Cl, S and P
to be less than 100 wtppm since such impurities will have an
adverse effect on the characteristics of ZnO. Preferably, the
amount of impurities is less than 10 wtppm.
[0029] Gas components of C, Cl and S must be sufficiently reduced
since these respectively form carbide, chloride and sulfide. It is
desirable that these are less than 100 wtppm. Among the above, in
particular, it is desirable that Cl is reduced as much as possible
since it increases the leakage current when the TFT is turned
off.
[0030] It is desirable that S is reduced as much as possible since
it deteriorates the mobility due to the scattering of impurities.
Further, C, Cl and S all cause the increase of particles during
sputtering.
[0031] Further, it is desirable that the Pb content is less than 5
wtppm since Pb deteriorates the electrical mobility due to the
scattering of impurities and has an adverse effect on ZnO. It is
desirable that the Mg content and Al content are respectively less
than 1 wtppm since Mg and Al have stronger oxidizing power than Zn,
deprive oxygen from ZnO, create oxygen loss, and further increase
the leakage current when the TFT is turned off.
[0032] Upon manufacturing high purity zinc oxide powder,
zinc-containing raw material is dissolved with acid at room
temperature, and thereafter subject to solvent extraction and
activated carbon treatment in order to remove impurities such as
organic matter and foreign matter and impurities such as Pb
described above. As the solvent, D2EHPA (D2 ethylhexyl phosphoric
acid) may be used.
[0033] Upon performing acid dissolution, any acid capable of
dissolving zinc may be used. As an example, acid leaching may be
performed with nitric acid. Or zinc may be dissolved via
electrolysis.
[0034] Thereafter, the resultant solution is neutralized with
alkaline solution to obtain high purity zinc hydroxide
(Zn(OH).sub.2). As the alkaline solution, in particular, it is
desirable to use ammonium hydroxide. The use of sodium hydroxide or
potassium hydroxide is undesirable since high concentrations of Na
and K will be respectively mixed in the zinc oxide.
[0035] The zinc hydroxide obtained as described above is fired at
100 to 500.degree. C. in order to obtain zinc oxide (ZnO) powder of
0.1 to 100 .mu.m. As a result of the foregoing processing steps, it
is possible to reduce various impurities, excluding gas components,
to be 1 ppm or less or 0.1 ppm or less, and obtain high purity zinc
oxide having a purity level of 5N or more. The flow of the
manufacturing method of high purity zinc oxide according to the
present invention is shown in FIG. 1.
[0036] This zinc oxide powder is further hot pressed and formed
into a sputtering target. As an example of the hot pressing
conditions, this may be performed under oxygen atmosphere at, for
instance, 1200.degree. C..times.5 hr.
[0037] This target is further sputtered under oxygen atmosphere to
obtain a high purity zinc oxide thin film.
EXAMPLES
[0038] Examples of the present invention are now explained. These
Examples are merely illustrative, and the present invention shall
in no way be limited thereby. In other words, the present invention
shall only be limited by the scope of the present invention, and
shall include the various modifications other than the Examples of
this invention.
Example 1
[0039] 100 g of raw material having a zinc content level of 90 wt %
and containing the impurities shown in Table 1 was subject to acid
leaching with 1 L of acid containing 10% nitric acid to obtain a
solution having a zinc concentration of 90 g/L.
[0040] Next, the resultant solution was subject to solvent
extraction with D2EHPA. This was further subject to activated
carbon treatment in order to remove impurities such as organic
matter and Pb. Thereafter, this was neutralized with NH.sub.4OH to
obtain high purity zinc hydroxide (Zn(OH).sub.2).
[0041] The obtained high purity zinc hydroxide was fired at
200.degree. C. to obtain high purity zinc oxide (ZnO) powder having
an average grain size of 10 .mu.m. The analysis of impurities of
the high purity zinc oxide is shown in Table 1.
[0042] As shown in Table 1, the various impurities listed in Table
1, excluding gas components, were respectively reduced to 1 wtppm
or less or 0.1 wtppm or less, and high purity zinc oxide powder
having a purity level of 5N or more was obtained thereby. A
significant improvement in purity was confirmed based on the
processing steps shown in Example 1 of the present invention.
[0043] This high purity zinc oxide powder was used to manufacture a
sputtering target by further performing hot pressing and sintering
at 1200.degree. C. for 5 hr under the flow volume of 5 ml/min of
oxygen gas. This target was sputtered under oxygen atmosphere, and,
in comparison to conventional targets, it was possible to form a
high purity zinc oxide thin film on the substrate. As the level of
particles on the thin film, there were 5 particles of 0.2 .mu.m or
larger.
[0044] The various impurities contained in the raw material are
particularly disfavored in the manufacture of semiconductor devices
and the like, and the reduction of these impurities is extremely
effective.
Example 2
[0045] The same raw material as Example 1 was used, and
electrolysis was performed with pH2 ammonium nitrate solution in
order to extract Zn in the solution. Impurities were removed with
the same method as Example 1. The impurities analysis and the like
are similarly shown in Table 1.
Example 3
[0046] The same raw material as Example 1 was used, and
electrolysis was performed with pH2 ammonium nitrate solution again
in order to extract Zn in the solution. Impurities were removed
with the same method as Example 1. The impurities analysis and the
like are similarly shown in Table 1.
Comparative Example 1
[0047] 100 g of raw material having a zinc content level of 90 wt %
and containing the impurities as with Example 1 was subject to acid
leaching with 1 L of acid containing 10% hydrochloric acid and 10%
hydrogen peroxide to obtain a solution having a zinc concentration
of 90 g/L.
[0048] NH.sub.4OH was added to this resultant solution and
neutralized to pH8 in order to obtain zinc hydroxide
(Zn(OH).sub.2).
[0049] This was further fired at 200.degree. C. to obtain zinc
oxide (ZnO) powder. The analysis of impurities of the obtained zinc
oxide is shown in Table 2.
[0050] As shown in Table 2, most of the various impurities shown in
Table 1 were hardly reduced. TABLE-US-00002 TABLE 2 Raw Comparative
Comparative Comparative Impurities material Example 1 Example 2
Example 3 Pb 100 80 20 <0.1 Fe 115 74 <0.1 <0.1 Cr 8 2 1.7
<0.1 Ni 6 5 4 <0.1 Cu 10 2 1 <0.1 Al 5 4 1 0.3 Cd 20 15 4
0.2 Sn 5 1 1 0.3 Sb 1 <1 <1 <0.1 W 1 <1 <1 <0.1
Tl 35 20 12 0.1 Mo 2 1 <1 <0.1 Ga 1 <1 <1 <0.1 Co 3
1 <1 <0.1 Mn 1 <1 <1 <0.1 Ti 4 2 <1 <0.1 K 5 3
2 0.5 Mg 13 10 7 <0.1 Na 80 70 40 150 B 10 4 1 <0.1 Li 50 40
15 <0.1 N 2000 850 1% 100 C 1% 700 5% 50 Cl 500 400 100 3 S 3%
1% 200 8 P 50 1 50 <0.1 Number of 700 1000 250 Particles
Comparative Example 2
[0051] 100 g of raw material having a zinc content level of 90 wt %
and containing the impurities as with Example 1 was subject to acid
leaching with 1 L of acid containing 10% hydrochloric acid and 10%
hydrogen peroxide to obtain a solution having a zinc concentration
of 90 g/L.
[0052] Next, the resultant solution was subject to solvent
extraction with D2EHPA to remove impurities. Incidentally, the
activated carbon treatment shown in Example 1 was not performed.
NH.sub.4OH was added to this resultant solution and neutralized to
pH8 in order to obtain zinc hydroxide (Zn(OH).sub.2).
[0053] This was further fired at 200.degree. C. to obtain zinc
oxide (ZnO) powder. The analysis of impurities of the obtained zinc
oxide is shown in Table 2.
[0054] As shown in Table 2, although the purity improved in
comparison to Comparative Example 1, impurities such as Pb, Tl, Na,
Li, Na, Cl, S and P were contained in a considerable amount, and
the effect of sufficiently removing impurities could not be
realized. Therefore, it is evident that activated carbon treatment
is important when compared with Example 1.
Comparative Example 3
[0055] 100 g of raw material having a zinc content level of 90 wt %
and containing the impurities as with Example 1 was subject to acid
leaching with 1 L of acid containing 10% hydrochloric acid and 10%
hydrogen peroxide to obtain a solution having a zinc concentration
of 90 g/L.
[0056] Next, the resultant solution was subject to solvent
extraction with D2EHPA. This was further subject to activated
carbon treatment to remove impurities such as organic matter and
Pb. Thereafter, this resultant solution was neutralized with NaOH
in order to obtain high purity zinc hydroxide (Zn(OH).sub.2).
[0057] This was further fired at 200.degree. C. to obtain high
purity zinc oxide (ZnO) powder. The analysis of impurities of the
obtained high purity zinc oxide is shown in Table 2.
[0058] As shown in Table 2, zinc oxide in which impurities
excluding Na and K equal to Example 1 was obtained. In particular,
the increase of Na is due to the neutralization with NaOH, and it
is evident that the use of ammonia water as the neutralizing agent
is important.
INDUSTRIAL APPLICABILITY
[0059] The present invention yields a superior effect in that high
purity zinc oxide can be manufactured at low cost by dissolving a
commercially available zinc-containing raw material having a purity
level of 90 wt % with acid, and thereafter subjecting this to
solvent extraction and activated carbon treatment in order to
effectively remove impurities, and is extremely useful as a target
material for electronic components such as a semiconductor
device.
* * * * *